Proper Protocol for Using Histofreeze (Cryotherapy) in a Clinical Setting
The proper protocol for using histofreeze (cryotherapy) in a clinical setting involves applying liquid nitrogen with a cotton-tipped applicator for 15-20 seconds until 1-2 mm of the circumferential skin around the target lesion appears frozen, followed by a 20-60 second thaw period, and then repeating the freeze step.1
Preparation and Equipment
- Ensure you have:
- Liquid nitrogen supply
- Cotton-tipped applicators or cryospray device
- Protective equipment for the operator
- Petroleum jelly or antibiotic ointment for post-procedure care
- Sterile dressings
Step-by-Step Protocol
Pre-Treatment Assessment
- Evaluate if the lesion is appropriate for cryotherapy
- Debride any overlying eschar down to a clean ulcer base
- Treat any secondary bacterial infection if present 1
- Avoid treating eyelids, lips, nose, and ears 1
Treatment Technique
- Disinfect the lesion and surrounding skin
- No anesthesia is typically required as it is not helpful for cryotherapy 1
- Apply liquid nitrogen using either:
- Cotton-tipped applicator for 15-20 seconds, or
- Cryospray directed at the lesion
- Continue freezing until 1-2 mm of the circumferential skin around the lesion appears frozen 1
- Allow thawing for 20-60 seconds 1
- Repeat the freeze step to complete one freeze-thaw cycle 1
Treatment Duration and Cycles
- For most dermatological conditions:
- Duration of freeze: 15-20 seconds
- For actinic keratosis: Longer freeze times (>20 seconds) yield higher cure rates (83%) compared to shorter durations (<5 seconds: 39% cure) 1
- Complete treatment may require:
- Single cycle for minor lesions
- Double freeze-thaw cycle for thicker lesions
- Repeat treatments at 3-week intervals until healing occurs 1
Post-Treatment Care
- Apply petroleum jelly or antibiotic ointment to the treated area
- Cover with a sterile dressing for several days 2
- Inform patients about expected reactions:
- Immediate: vesicle formation, erythema, swelling, burning pain
- Delayed: hypo- or hyperpigmentation (worse in darkly pigmented skin)
- Resolution of pigmentation changes typically occurs within 6-12 months 1
Clinical Considerations and Contraindications
Best Candidates for Cryotherapy
- Small, recent-onset, uncomplicated lesions
- Actinic keratosis (especially on face and scalp)
- Cutaneous leishmaniasis (small lesions <30mm width) 1
- Bowen's disease (with appropriate technique) 1
Contraindications
- Lesions with risk of mucosal dissemination
- Lesions with associated nodular lymphangitis
- Immunocompromised hosts 1
- Areas with poor circulation
- Patients with cryoglobulinemia or cold urticaria
Potential Complications and Management
- Immediate reactions: vesicles, erythema, swelling, burning pain
- Delayed reactions: hypo/hyperpigmentation, scarring
- Serious complications (rare with proper technique):
- Secondary infection: treat with topical antibiotics
- Scarring/keloid formation: more common with repeated treatments
- Nerve damage: avoid treating areas with superficial nerves
Efficacy Considerations
- Success rates vary by condition:
The success of cryotherapy is highly dependent on the operator's skill and complete, careful application. It is crucial to treat into normal-appearing tissue around the lesions to ensure complete coverage of the pathological area 1.